We are identifying families in which multiple first-degree members have a diagnosis of obsessive-compulsive disorder (OCD). These families are being identified from any source, including referrals from Johns Hopkins clinicians and private therapists in the community. If they are willing to come into the clinic, the subjects are being examined by GCRC personnel; otherwise, they are being examined by psychiatrists and clinical psychologists. The aim of the study is to clinically evaluate all the first-degree family members and to obtain a blood sample from each. Cell lines for future DNA extraction are being developed. To date, we have clinically examined 11 subjects identified in this manner, and obtained blood samples from them. Once an adequate number of subjects has been examined, we will be poised to proceed to genetic studies of these families, including both linkage and association strategies. The ultimate goal is to identify gene(s) involved in the development of OCD. This will help clarify the pathophysiology of the condition and lead to more rational treatments.